 <style type="text/css">

 .mainBg
 {
 width:100%; /*设定层的宽度*/
 margin:auto; /*层居中*/
 height:100%; /*设定高度*/ 
 clear:both /*清除浮动*/
 background-color:EDEDED;
 text-align:center;
 }
 </style>
 <div class="mainBg"  >
      <img src="${cache}/images/homepage01.jpg" border="0"/>
 </div>